The invention relates to a display device comprising an electro-optical material between two substrates of which at least one substrate is transparent, and a first substrate is provided with picture electrodes, in which each picture electrode is coupled via a switching element to a row electrode and a column electrode, and in which the picture electrode is capacitively coupled to a further electrode. The device further comprises drive means for providing the row electrodes with a selection signal and the row electrodes or the further electrode with a bias signal.
In this application, the term "capacitively coupled" is understood to mean that there is a coupling via an (auxiliary) capacitance, for example, by (partial) overlap of a picture electrode associated with a row and a part of the row electrode associated with a subsequent (or previous) row.
The second substrate may be provided with electrodes too (counter electrodes) defining at overlapping areas (a matrix of) picture elements. Picture elements may also be defined by picture electrodes in the same substrate (in plain switching).
Such display devices are used in, for example television and monitor applications.
A display device of the type mentioned in the opening paragraph is described in EP-A-0 657 864. This document describes how a DC component across the liquid crystal material is prevented in a liquid crystal display device by adaptation of a selection signal. To this end, the selection signal consisting of a gate pulse is extended with so-called gate-bias voltages applied during a gate-bias period. Where the selection signal is referred to in this application, the signal is understood which causes the switching element to conduct (generally the actual gate pulse of a TFT transistor). Where a bias signal or voltage, "(gate)-bias signal" or "(gate)-bias voltage" are mentioned, a bias signal or bias voltage as described in EP-A-0 657 864 is referred to, and therefore not the voltage across a row electrode during non-selection although when the gate-bias signal is presented to a selection electrode, although during a gate-bias period such a gate-bias signal may temporarily have a level which is equal to that of a non-selection signal. Instead of being presented to a row electrode, the bias signal may also be presented, for example, to a common connection for a number of capacitances within one row.
Due to the capacitive coupling between a picture electrode with an adjacent row electrode, it is true that the speed of the display device is considerably increased, but at this speed (and hence the transmission to be reached within one field period) flicker and artefacts (in moving images) still appear to occur frequently.